Circulatory System Flashcards
Why do we need a circulatory system?
the surface area to volume ratio is not large enough for diffusion alone to supply sufficent nutrients (oxygen, glucose and other molecules) to the body
Name what makes up the human circulatory system.
- Artium
- Ventricle
- Bicuspid valves
- Tricuspid valve
- Aorta
- Pulmonary Artery
- Pulmonary Vein
- Vena Cava
Why is the heart described as myogenic?
because it has the ability to initiate it’s own contractions
Explain how the heart initiates it’s own contractions.
- sinoatrial node creates wave of excitation
- wave reaches atrioventricular node
- wave moves down bundle of His
- Bundle of His attaches to Purkyne fibres which carries the wave to the apex of the heart
- this causes ventricules to contract
What is the purpose of the sinoatrial node?
it acts as the heart’s pace maker
Where is the atriventricular node?
between the two atria
Why does the ventricles contract after the atria?
because the septum at the base of the atria can’t conduct
Why does the ventricle contract at the ape of the heart?
it allows blood to be forced upwards, out of the aorta and pulmonary vein
What are the 3 stages of the Cardiac Cycle?
- Cardiac Distole
- Atrial Systole
- Ventricular Systole
What happens during the Cardiac Distole?
- artia and ventricles relax, which keeps semi-lunar valoves closed
- elastic recoil lowers the pressure in the chambers
- blood returns through pulmonary vein and vena cave which increases pressure
- this forces atrioventricular valves open
What happens during the Atrial Systole?
atria forces remaining blood into ventricles by contracting
What happens during the Ventricular Systole?
- atrioventricular valves open and semi-lunar valves close because the ventriles contract
- this allows blood to leave the left ventricle (through the aorta) and the right ventricle (through the pulmonary artery)
